New comment by Gottox on void-packages repository

https://github.com/void-linux/void-packages/pull/24026#issuecomment-733803546

Comment:
From the documentations it looks like those are gcc builtins:

```
man outb
...
You must compile with -O or -O2 or similar.  The functions are defined
as inline macros, and will not be substituted in without optimization
enabled, causing unresolved references at link time.
...
```